Highly integrated semiconductor chips, or modules and the like in which they are disposed on a substrate with a high density, have been used to control a variety of appliances. Devices such as semiconductor chips should be usually used in a predetermined service temperature range, and malfunction when they are used beyond the range. Accordingly, it is necessary to appropriately radiate the heat generated by semiconductor chips and so forth. In particular, the higher the degree of integration is, or the more the control currency magnitude increases, the more it is necessary to enhance the cooling capacity. Hence, it has been carried out conventionally to dispose radiator members such as heatsinks on the bottom surface of semiconductor chips or substrates.
Such radiator members are required to exhibit high thermal conductivity in order to improve the radiating ability and low thermal expandability and in order to suppress the cracks (for example, solder cracks) between radiator members and the semiconductor chips or substrates as well as the thermal strain of radiator members themselves. However, it is impossible for ordinary metallic materials such as aluminum to fully satisfy both of the characteristics which are in a trade-off relationship.
Meanwhile, when Si-based ceramic materials such as SiC are used in radiator members, it is possible to satisfy both of the characteristics at a higher order. However, ceramic materials such as SiC are poor in terms of the toughness, and are weak against shocks. The radiator members might crack, break and the like by shocks which are applied to the radiator members in processing, assembling, using and so forth.
Hence, metal-ceramic composite materials have been used in radiator members in order to satisfy the high thermal conductivity, low thermal expandability, high reliability and the like in a well balanced manner. For example, in Japanese Unexamined Patent Publication (KOKAI) No. 11-228,261, a metal-ceramic composite material for heat sinks is disclosed in which an SiC powder having a predetermined average particle diameter is dispersed in an Al—Si—Mg matrix meal. Specifically, a composite material is disclosed in which one type of an SiC powder whose average particle diameter is 20 μm approximately is dispersed (or filled) in the matrix metal in a proportion of from 60 to 70% by volume. However, the thermal conductivity of this composite material is no more than 180 W/(m·K) only.
Moreover, Japanese Unexamined Patent Publication (KOKAI) No. 11-106,848 discloses a composite material in which two types SiC powders whose average particle diameters differ are dispersed in an Al alloy. Specifically, a composite material is disclosed in which an SiC powder whose average particle diameter is 50 μm and an SiC powder whose average particle diameter is 14 μm are dispersed in an Al alloy in a proportion of from 40 to 70% by volume. However, the thermal conductivity of this composite material is also no more than 180 W/(m·K) only.